Method of and apparatus for heat treating



Sept. 22, 1942.

A. C. DAVIDSON METHOD 0F AND APPARATUS FOR HEAT TREATING Filed Feb. 7, 1940 R. o T0 w 5W W /C f W M M 8217.2

Patented Sept. 2.2,l 1942 2,298,380 METHOD GF AND APPARATUS FOR BEAT TREATING Arthur C.

Davidson, Canton, Conn.: Avis Colo Davidson, executrix of said Arthur C. Davidl son, d

Application February .7, 1940, Serial No. 317,708

18 Claims.

My invention relates to methods oi and apparatus for heat treating.

It has among its objects to provide an improved method of heat treating whereby it is made possible to control the atmosphere surrounding the work in such manner as to obtain markedly improved results. A further object is to provide such an improved method whereby it is made possible to insure the provision of the desired carbonaceous or non-oxidizing atmosphere surrounding and in contact with the articles to be treated, regardless of the furnace atmosphere. Another object of my invention is to provide an improved method whereby it is made possible to control this atmosphere as desired as regards circulation, pressure, and air and gas content, and in such manner as to avoid decarbonizing or defacing or scaling 'of the surfaces of the articles while eliminating all necessity for packing the latter in carbonaceous orother protective materials. An additional ob- `iect 'of my invention is to provide such an improved method whereby, by suitably controlling the circulation in the article containing chamber, it is made possible either to heat the articles for quench hardening or, while still using the same container, to effect carburizing. A still further object of my invention is to provide such an improved method which is adapted to be carried out in any furnace while definitely improving the results obtainable and enabling the same to be obtained with markedly increased certainty, irrespective of wide variation in the chemical composition of the iron or steel to be treated, and While making oxidation or decarburization impossible, regardless of the furnace atmosphere. Another object of my invention is to provide improved apparatus adapted to carry out my improved method and including improved means for generating the desired non-oxidizing atmosphere and circulating and controlling the ow thereof to produce the desired effects on the articles treated. Other objects of my4 invention are to provide such an improved container which is adapted for use in any furnace and to maintain the desired atmosphere in contact with the articles irrespective of the furnace atmosphere, and one which is further adapted to be used either to eilect heating of the articles for quench hardenmg or to effect carburizing as may be desired, 50

while, in either use, eliminating all need for packing the articles in. carbonaceous material. Still other objects of my invention include the provision of s ch a container of an improved construction, including an improved chamber for carbonaceous material, an improved cooperating and communicating Vchamber for the articles to be treated vwherein the latter are disposed out of contact with said material, and improved control means for controlling either the air supply to the carbonaceous material or the escape of gas from the article chamber. These and other objects and advantages of my improvements will, however, hereinafter more fully appear.

In the accompanying drawing, I have shown for purposes of illustration certain embodiments of apparatus which are adapted to use in carrying out my improved method.

In this drawing: y

Figure 1 is a vertical sectional view of a furnace showing certain of my improved containers therein;

Fig. 2 is an enlarged vertical section on line 2-2 of Figure 1;

Fig. 3 is a top plan view of the construction shown in Figure 2, certain portions being broken away to facilitate illustration;

Fig. 4 is a bottom plan view of the construction shown in Figure 23 Fig. 5 is an enlarged vertical section corresponding to Figurev 2 and showing a modified construction;

Fig. 6 is an enlarged top plan view of the construction'shown in Figure 5, certain portions bemg broken away to facilitate illustration;

Fig. 7 is an end elevation of a further modified container construction;

Fig. 8 is a longitudinal section on line 8-8 of Figure 7, and

Fig. 9 is a transverse section on line 9-9 of Figure 8.

In the practice of my invention, my improved method is carried out in an improved container, generally indicated at i in Figure 1, and supported on feet 2 above the bottom 3 of a heating chamber l of an ordinary oil or gas fired heat treating furnace 5 of any suitable form and having any usual control connections 6, and usual supply connections (not shown) opening into the chamber 4, and an upper outlet or vent 'l for the latter.

Referring to the container l, it will be noted that this container, while obviously capable of assuming other shapes, is shown as a round container in this illustrative construction. As shown in Figures 2 to 4, it is also of an improved sectional and vertically separable structure and includes an improved bottom gas generating element and an improved top article carrying elef ment, together with improved flow controllin means on both elements.

'Ihe bottom element or member 8 hereinencloses a chamber 9 for carbonaceous material therein which is of sufcient depth to contain a substantial charge of any suitable carbonaceous material distributed over the bottom thereof. Further, it will be observed that the feet 2 on this member 8 serve to space the bottom thereof from the furnace bottom 3 in such-manner as to permit a free Icirculation of the furnace atmosphere between these feet 2 and up through a bottom valve I 0. Herein, this valve is of rotatable disc form and has a suitable operating handle II and suitable spaced holes or openings I2 therein, in such manner as to enable it to control the air flow through cooperating upwardly and outwardly directed passages I3 in the bottom of the member 8. While a at bottom may Y be used if desired, a centrally located raised bottom portion I4 is herein provided on the member 8 having these passages I3 therein and carrying the lvalve III. In practice, the openings I2- and I3 may vary widely in size and arrangement and the form of valve mayl also be varied, but it will be understood that it is intended that the air lintake through such openings I2 and I3 may be varied or entirely cut off, as desiredhby suitably .moving the disc valve I0 relative thereto.

" `liurther, .itv will be noted that the air passing through any openings I2 in the disc Il)v and any this member I1 herein is also provided with holes I8 distributed over the same, as, for example, shown in Fig. 3, in such manner as thereby not only to permit the upward flow of .the gases rising from the carbonaceous material, but also to distribute the gases with substantial uniformity through the grid I1. Here, it willv also be observed that the upper surface I9 of this grid is indented at the mouth of the openings I8 and provided with rounded portions therebetween, in such manner as to minimize the area in contact with the articles carried on this surface. It will also be observed that the grid I1' is freely bodily removable vertically from the flange. I6 and is spaced inwardly from `an upwardly projecting outer flange on the base 8 which extends substantially above this grid, while an outer ange 2| is also provided on the member 8 around the base of the upstanding flange 2,8. Thus, it will be evident that the articles to be treated may be supported, if desired, onl the grid I1, the same .preferably being stacked in such a formation ywith a' loose t in a suitable groove in the flange 2|, 'and herein the memberA z2 also extends a 4substantial distance above the upper end of the upstanding flange 20 on the member 8 While being spaced therefrom. As shown, this cover member 22 has a series of holes or openings 24 distributed over a dat top and corresponding generally to the holes IB and likewise subject =to wide variation in size and arrangement. Herein, however.'4 it will be noted that these holes are disposed annularly around a central valve carrying portion '25, and thata rotatable valve disc 26 carrying similar holes 21 is supported on the upper surface of the cover 22 and suitably connected thereto by a wing nut 28 above valve disc provided on disc 26 to facilitate movement' thereof. y

In practicing my improved method during quench hardening, the chamber 9 is suitably lled with carbonaceous material I5 and the articles to be heat treated are suitably arranged or stacked on the grid I1 while the cover 22 is removed. 'I'he latter is then put on and, while Y leaving all jointsunsealed so that gas may escape and provide further free circulation, the container I is placed in the furnace 5 as shown in Figure 1; the vvalve discs I8 and 26 being suitably adjusted to effect the desired iiow of airthrough the carbonaceous material and the desired iiow of gas generated by the carbonaceous material during heating and passing up through the holes I8 in the grid I1 and around the article supported on the latter and through ports 24, 21. Accordingly, through the adjustment of one or both of these disc valves and with the carbonaceous material in the chamber 9, it is made possiblenot only to control the gas mixture but further to insure the desired circulation of the same in such manner as to cause the gas to be in contact with all surfaces of the work. Thus, the desired carbonaceous or non-oxidizing atmosphere is obtainable and maintainable throughout the heating operation, irrespective of the furnace the articles through scaling or the like. In practice, the existence of a non-oxidizing gas is indicatedv by the bluish flameissuingv through the openings 21 in the disc 26 at the top of the container I. e

Whenever it is desired to carburize or caseharden the articles, tl ie loose fit between the ange 23 on the cover 22 and the flange ZI on the member 8 is suitably sealed, as by applying a iire clay seal 30. Further, the top valve 26 is moved in such manner as substantially to prevent the escape of carbon gas. Preferably,it is opened only to such a small extent as to permit the operator to observe that sufllcient gas is escaping to avoid excess pressure capable of moving the cover. Under suchconditions, the carbon gas around the articles will cause carbide absorption or so-called carburization or. casehardening on all of the surfaces of the articles heated.

It `win be evident that through the use of the top and bottom valve mechanisms it is made possible to vary the atmosphere inside the container accesso to meet widely different conditions while eliminating atmospheric stagnation therein. For example, in heat treating tool steel for hardening quench, the top valve is fully opened while the bottom valve is opened only a small amount in such manner that the pressure inside the container is then equivalent to the pressure in the furnace. If, onv the other hand, a low carbon steel is to be carburized, with the same amount of carburizing material in the container it is possible to obtain the desired carburizing effect by a suitable reverse adjustment of the valves, the bottom valve then being opened wider than the top valve. Accordingly, a sufficient air intake is provided to insure satisfactory circulation, thus avoiding stagnation and resultant surrounding of the parts to be treated with unspent carbonaceous gases, while insuring acontinuous supply of the desired mixture of generated gas and furnace atmosphere around the exposed articles to be treated.

Referring to the modified form f my invention shown in Figures and 6, the structure therein is essentially similar to that heretofore described and also capable of carrying out my improved method. Herein, however, it will be observed that, as distinguished from a grid I1 in disc form, a generally similar grid 3i is integrally united to the bottom of an upper article container 32 supported on an inwardly extending flange 33 on a bottom member 34 having only an outer upstanding flange 35 thereon and otherwise similar to the bottom member 8 heretofore described. In this construction, the container 32 is also provided with an open top 36 and with an outer flange 31 adapted to receive a depending flange 33 on a cover member 39 perforated to correspond to openings 24 and carrying a cooperating perforated disc valve corresponding to valve 26 heretofore described. In this construction, it will be evident that the articles may be suitably stacked in the member 32 before the latter is placed on the member 34, a feature which is desirable in certain work. Here, also, it will be evident that my improved method may be practiced as above described during heating for quench hardening, the member 32 and flange 38 then having loose fits in the flanges 35 and 31 to permit the escape of the'carbon gas during such an operation, while during carburizing a suitable ire clay seal is applied to these joints and the upper disc valve suitably adjusted to develop the desired pressure, all as hereinabove described.

In Figures 7, 8 and 9, a furthermodiiied construction is illustrated, wherein a horizontal cylindrical member 40 is utilized enclosing a corresponding article chamber 4| having holes 42 in its lower side communicating with an elongated lower chamber 43 for carbonaceous material. Further, it will be observed that herein suitable holes 44 are provided in the upper side of the cylindrical member 40, and that a longitudinally movable perforated valve member ,45 is provided to eifect the desired control of the escaping carbon gas. Obviously, in this structure, my improved method may be practiced in generally similar manner during heating for quench hardening or carburizing this apparatus being especially adapted to permit the application of the same to long cylindrical articles such, for example, as golf shafts or the like, which are disposed in horizontal relation in the chamber 4I. Obviously, such a longitudinally sliding valve may also be used with other forms of containers where the shape of the latter is such as to makesuch sliding movement-desirable, as compared with the previous rotating .or disc type valves, as, for example, where1 the container is rectangular in shape, as may be preferred for certain articles.

As a result of my invention, and the resultant controlled non-oxidizing atmosphere, it is made possible to obtain a new and definite control or the carbon gas and of its circulation, in such manner as to enable not only an improved product to be obtained, but also to enable the same to be obtained with greater certainty. At` the same time, it'is made possible to eliminate altogether the need for packing the articles to be heat treated in the carbonaceous material, and further to eliminate the variations in the product resulting from either variations in the operation of the furnace or variations in the disposition of the carbon or irregularities in the contact of the carbon with the articles. Thus, for example, it is made possible to eliminate the previous dinicuities due to enlarged or microscopical areas absorbing less carbides and consequently having a dissimilar speed of quenching velocity resulting in soft spots, and also to eliminate the embrittling of other areas due to constant contact with live` carbonaceous material, and resulting in an overabsorption of carbides in such manner as thereby to increase the carbon content over that required for quenching at the predetermined temperature. Attention is further directed to the fact that my improved control of the carbon gas makes wholly unnecessary either the use of a gas curtain at the furnace door entrance, or the employment `of carbon vapor in the furnace proper, vwhile also substantially reducing the extent to which the surfaces of the work become decarburized and defaced through oxidation when using such a curtain,- and further avoiding the tendency of the oversaturated carbonaceous atmosphere in vapor furnaces to form an embrittled surface area resulting in surface cracks and peeling and cracks when the articles treated are stressed in operation.

Attention is also directed to the fact that my improved container structure is of a character adapted to be readily and inexpensively provided, while enabling the above advantageous results to be obtained, and while further being adapted to use in any furnace. The construction is also such that the same container may be used, if desired,

either for quench hardening or carburizing or casehardening, without any change in the container structure and entirely depending upon the character of the heat treating process which it is desired to perform, thereby substantially reducing the necessary expense for equipment. It will also be evident that the structure is such as to lend itself readily todifferent shapes' and dimensions of the article containing chamber, adapting it to heat treating articles of widely different character. It will further be evident that the valves may be readily adjusted before or during heating as desired. The provision of the raised bottom valve structure is such as to facilitate insertion or removal of the container or pots while minimizing valve handle breakage. Such a structure, by reason of its generally concave formation, also permits greater concentration of temperature in the center of the container and thereby insures greater thermal uniformity. These and other advantages of my improvements will, however, be apparent to those skilled in the ar While I have herein speciiically described certain forms of my invention, it will be understood 'Y etherein with the atmosphere in the furnace, and

l controlling the flow :of furnaceatmosphere through said container to control the atmosphere in the latter acting on the articles.

2. The method of heat treating metal articles in a portable article container also containing non-oxidizing gas generating material which consists in, inserting the loaded container in a furnace generating its own atmosphere, generat- `ing a non-oxidizing gas from said material in said container by passing a ow of furnace atmospherethrough said material while the latter is out of contact with said articles and the resultant mixture is in contact with exposed articles therein, and yeffecting a controlled flow of furnace atmosphere through said container to l control the atmosphere therein. y

3. The method of heat treating metal articles non-oxidizing gas generating material which consists in, inserting the loaded container in a aacas'eo material in the article container out of contact I with the articles therein', and circulating around exposed articles in saidy container a controlled mixture of furnace atmosphere passing through said material during heating and of gas gen. 1

erated by said material, while -permitting substantially free escape of said mixture from said container. I

-7. 'I'he method of heat treating metal articles in a portable article container which consists in,- inserting the loaded container-in a furnace genv erating its own atmosphere with the articles in in a portable article container also containing furnace generating its own atmosphere. generatsaid container by passing a flow of furnace atmosphere upward through said material while the latter is out of contact with said articles and t-the resultant mixture rises and escapes after contact with exposed articles therein, and controlling the ow of furnace atmosphere through said container to control the atmosphere therein. 4. The method of heat treating metal articles in a portable article container which consists in, inserting the loaded container in a furnace generating its own atmosphere with the articles in said container anda supply of gas generating material in said container out of contact rwith the articles therein, passing the furnace atmosphere through said material during heating while heating said container in `-the furnace, and circulating a controlled atmosphere comprising a mixture of furnace atmosphere and of gas generated'by said material around said articles and out of said container.

5. The method of heat treating metal articles and of the gas generated by said material during heating, and controlling the escape of said mixture from the container and the intake of fur- M-r'nace atmosphere through said material to control the atmosphere in the container.

6. The method of heat treating metal articles in a portable article container which consists in, inserting the loaded container in a furnace generating its own atmosphere with the articles in said container and a supply of gas generating said container and a supply of gas generating material in the article container below and out of contact with the articles therein, and distributing aroundA exposed articles in said container a controlled'- mixture of furnace atmosphere passing through said material during heating and of gas generated by said material during Vheating while controlling the escape of the mixture` from said container to control pressure therein.

8. A heat treating pot insertable with its charge into a furnace and having in said pot and movable bodily therewith non-oxidizing gasgenerating means including a lower ,chamber for gas generating material, article containing means forming a part of and movable bodily with said pot Aand above said chamber including a grid forming a cover for said gas generating chamber and supporting the articles out of contact with said material, and mixture controlling means on said pot adjustable prior to insertion of the charged pot into the furnace and movable bodily therewith for maintaining the articles in said Ycontaining means surrounded by a controlled mixture of furnace atmosphere and the gas generated in rsaid chamber during heating.

9. A heat treating pot insertable with its charge into a furnace and having in said pot and movable bodily therewith non-oxidizing gas generating means including a lower vchamber for gas generating material, article containing means forming a part of and movablel bodily with said pot and within the latter and above said chamber including a grid forming a cover for said gas generating chamber'and supporting the articles out of contact with said material, and mixture controlling means on said pot `adjustable prior to insertion of the charged pot into the furnaceand movable bodily therewith during insertion for maintaining the articles in said containing means surrounded by a controlled mixture of furnace atmosphere and the gas generated'in said lower chamber during heating including valve mean-s for effecting a controlledl escape of the mixture from said article containing means.

10. `A heat' treating pot insertable with its charge into a furnace and having in said pot and movable bodily therewith non-oxidizing gas generating means including a chamber for gas generating material, article .containing means forming a part of and movable bodily with said pot above-said chamber including a grid forming a cover for said'gas generating chamber and sup-- porting the articles out of contact with said material, and means including inlet and outlet valves on the bottom and top of said pot adjustable prior to insertion of the charged pot into the furnace and movable bodily therewith during insertion for effecting a controlled ow of fur'- nace atmosphere through the material in said chamber and a controlled flow of a mixture of azaaeso said atmosphere andthe generated gas from said chamber .about the articles on said grid.

11. A heat .treating container insertable in a furnace and having therein non-oxidizing gas generating means including a chamber for gas generating material, article means carried by said container ,above said chamber including a grid for supportingJ the articles out of contact with said material, and means including perforated disc valve, mechanisms of large area on they bottom of said chamber and on the top of said container, for effecting a controlled iiow of furnace atmosphere through the material lin said chamber and a controlled flow of a mixture of said atmosphere and the generated gas from said container.

12. A heat'treating container insertable in a furnace and having therein non-oxidizing gas generating means including a chamber for gas generating material, article containing means carried by said container and including a grid supporting articles within the latter andabov'e said chamber out of contact with said material,

and having a chamber for gas generating material carried by and movable bodily with said pot and having an air valve in its bottom, article enclosing means carried by and movable bodily with said pot above said chamber and having a grid spacing` the articles out of contact'with said material and also having chamber forming means above said grid, and valve means on the top of said chamber forming mean-s and movable bodily with said container for controlling the escape of gases therefrom, said first mentioned chamber having a raised bottom portion projecting -upwardly into said gas generating 'material and said air valve being carried on said raised portion.

14. A heat treating pot insertable with Aits charge into a furnace and having a 'chamber for gas generating material forming a part of and movable bodily with said pot and said chamber having an air valve in its bottom, article enclosing means forming a part of and movable bodily with said pot above said chamber and including a grid spacing the articles out 'of contact with said material and also including chamber forming means above said grid, and valve means on the top of said chamber forming means and movable bodily with said container for controlling the escape of gases therefrom, said aixgvalve, grid and valve means being vertically spaced one above the other in said pot and having means for effecting a substantially uniformly distributed flow through said chamber forming means and around articles on said grid.

15. A heat treating container insertable in a furnace and having a chamber for gas generating material carried by and movable bodily with said container and having an air valve in the bottom of said chamber for controlling the flow of furnace atmosphere through said material, article supporting means carried by andv movable bodily with said container above said cham'- ber and having a grid spacing the articles out of contact with said material and also having chamber forming means above said grid, and valve means on the top of said chamber forming means and movable bodily.with said container for controlling the escape of gas from said chamber, said grid and chamber forming means being separable.

16. A heat treating container insertable vin a furnace and having a chamber for gas generating material carried by and movable bodily with said container and having an air valve in the bottom of said' chamber for controlling the flow of furnace atmosphere through said material, article supporting means carried by and mov.- able bodily with said container above said chamber and having a grid spacing the articles out of contact with said material and chamber forming means above said grid, and valve means on the top of said chamber forming means and movable bodily with said container for controlling the escape of gas therefrom, said grid being fixed to and forming the bottom of said chamber forming means and being removable therewith.

. 17. A heat treating container insertable in a furnace and having a chamber for gas generating material carried by and movable bodily with said container and having an air valve in the bottom 0f said chamber for controlling the iiow of furnace atmosphere through said material,

article supporting means carried by and movable 18. A heat treating container having elongated chamber forming means for gas generating material, an air valve in the bottom thereof for controlling the ilow of furnace atmosphere through said material, an elongated article receiving chamber having a grid in its bottom side spacingv the articles out of contact with said material and having a perforated upper' side, and an adjust- Y vable valve on said `upper side for controlling the flow through theperforations therein.

ARTHUR C2.4 DAVIDSON. 

